Fitting new patio door, correcting opening size, mortar bed thickness?

[Del-inquent]

I'm just giving my brother a hand getting ready for a new patio door to be installed. The manufacturer has sent the spec and sizes over. Due to the way it's specced (to give an almost flush cill to the inner floor level) and to match another patio door nearby, a row of bricks needs to be removed at the bottom of the opening. The door spec requires 10mm tolerance all round, however removing the full course of bricks gives too much clearance - with 10mm above the door, there will be 35 - 50 mm below (lowest course of bricks is not level, old house)

I'm thinking of just laying down a bed of mortar on top of the newly revealed course, running from 25mm one end to 40mm other end, to level it and create the correct dimension. Any flaws in that plan? Mortar work is "not my strong point" so thought I'd check. We're not fitting the door, the supplier is, so I don't want them turning up and saying it's not suitable for reasons I've not thought of.

[gaz_moose]

could you buy a knock-on and sit it on that?  probably wont knock in if you have opted for low threshold

 

Wickes White uPVC Frame Extender - 20mm x 1850mm | Wickes.co.uk

 

obviously not from wickes, they do them inaluminium if your door is mega heavy.

[Dave Jones]

use conc not muck.